1. Field of the Invention
The present invention relates to a drive device adapted for allowing the drive shaft to undergo displacement by using electromechanical transducing element (electromechanical transducer) so that driven body can be moved along the drive shaft, and a recording and/or reproducing apparatus using such a drive device.
The present application claims priority of Japanese Patent Application No. 2001-390184, field on Dec. 21, 2001, the entirety of which is incorporated by reference herein.
2. Description of the Related Art
Disc reproducing apparatuses using optical disc which is disc-shaped recording medium as recording medium have been used. The disc reproducing apparatus of this kind comprises a disc rotation drive mechanism for rotationally driving optical disc on which information signals are recorded, an optical pick-up for carrying out read-out of information signals recorded on the optical disc rotationally driven by this disc rotation drive mechanism, a supporting mechanism for movably supporting this optical pick-up in radial direction of the optical disc, and a drive mechanism for allowing the optical pick-up supported by this supporting mechanism to undergo feed operation in the radial direction of the optical disc. These mechanisms are assembled into base disposed within a casing constituting the apparatus body.
The disc rotation drive mechanism includes a disc table integrally attached at the drive shaft of a spindle motor. Optical disc is loaded on the disc table so that it can be rotated in one body therewith. The optical pick-up comprises a light source for emitting light beams, an object lens (objective) for converging light beams emitted from the light source onto signal recording surface of the optical disc to irradiate them, a light receiving element for detecting return light beams reflected from the signal recording surface of the optical disc, and a biaxial actuator for allowing the object lens to undergo displacement drive in a focus direction of the optical axis direction and in a tracking direction of plane surface direction perpendicular to the optical axis direction on the basis of a focus error signal and a tracking error signal which are obtained on the basis of return light beams detected by the light receiving element. The optical pick-up converges light beams emitted from the light source by the object lens, and carries out a control so that light beams thus converged are caused to be in-focus state on the signal recording surface of the optical disc and follow recording tracks of the optical disc to carry out readout of information signals recorded on the optical disc.
Such an optical pick-up is supported by the supporting mechanism. The supporting mechanism comprises a supporting base for supporting the optical pick-up, and a main shaft and a sub-shaft which movably support this supporting base in radial direction of the optical disc. The drive mechanism includes a rack member provided on the supporting base, gear mechanism composed of gears and feed screw, etc. which are meshed with this rack member, and a drive motor for rotationally driving these gear mechanisms to move the rack member in a direction along with the main shaft and the sub-shaft. When the drive mechanism is driven, the optical pick-up is moved in the radial direction of the optical disc as the result of the fact that the supporting base is moved while they are guided by the main shaft and the sub-shaft.
Since such disc reproducing apparatus requires a large number of gears at the drive mechanism, the number of parts (components) is increased so that the assembling step would become complicated. Because the number of parts is many, it is difficult to realize further miniaturization of the apparatus itself.
Meanwhile, as a drive device for driving driven body, drive devices using electromechanical transducer have been conventionally proposed and used. Such drive devices comprise a drive friction member which is caused to undergo by the electromechanical transducer, and a drive circuit for driving the electromechanical transducer. The drive device is adapted so that when a lamp voltage of a predetermined period serving as drive voltage is applied from the drive circuit to the electromechanical transducer, it allows the drive friction member to undergo displacement to move driven body attached to this drive friction member along the drive friction member. Since such drive device does not require gear, etc. at the mechanism for moving driven body, the number of parts can be reduced. Thus, miniaturization of equipment using such device can be realized.
By using such drive device using electromechanical transducer at the movement mechanism for optical pick-up of the above-described disc reproducing apparatus, the number of parts of the disc reproducing apparatus is reduced so that miniaturization of the entirety of the apparatus can be realized. In this case, by replacing either one of the main shaft and the sub-shaft which constitutes the supporting mechanism for the optical pick-up by the drive friction member for the drive circuit to allow this drive friction member to undergo displacement by the electromechanical transducer, the optical pick-up can be moved in the radial direction of the optical disc.
However, there is also the possibility that the disc recording/reproducing apparatus is not used for a long time. In such a case, there are instances where friction force with respect to the drive friction member of the optical pick-up changes, and particularly friction force becomes too large. When friction force has become large in this way, there is the possibility that the optical pick-up may not be smoothly moved in the radial direction of the optical disc at the time of starting. Particularly, with respect to portable type disc reproducing apparatus, there are instances where such apparatuses are carried to various places by user and are exposed to the environment of low temperature or high temperature, or high humidity or low humidity. When the disc reproducing apparatus is exposed to such environment, friction force with respect to drive friction member of the optical pick-up becomes too large similarly to the above-described case, so the optical pick-up cannot be smoothly moved in the radial direction of the optical disc at the time of starting.